[b1_ana] draft proposal

[Elena Long]

What constitutes a small angle? Less than 20 degrees? 10 degrees?

Take care,
Ellie

Elena Long, Ph.D.
Post Doctoral Research Associate
University of New Hampshire
elena.long at unh.edu
ellie at jlab.org
http://nuclear.unh.edu/~elong
(603) 862-1962

On Fri 03 May 2013 03:10:19 PM EDT, J. P. Chen wrote:
> Hi, Oscar and Karl,
>
> I just saw Alexandre and asked him to take a look at our data
> (Pengjia probably would be better, but he is in China and time
> zone makes it difficult to get him now).
>
> One more systematics: The acceptance will change slightly with
> the target magnet field. Since the scatter electron path will be
> not along the target field (longitudinal) direction, the spectrometer
> will be the regular (S)HMS+ target field. The effect is small for
> small angle (but probably not negligible) and increases for large
> angle. This should be looked into.
>
> Cheers.
>
> Jian-ping
>
>
> On 5/3/2013 2:49 PM, O. A. Rondon wrote:
>> Hi JP,
>>
>> That is good news. I think we should put some kind of reference or quote
>> some numbers in the proposal, so the TAC and PAC know about it, although
>> the TAC may know already.
>>
>> Cheers,
>>
>> Oscar
>>
>> J. P. Chen wrote:
>>> Oscar,
>>>
>>> The BCM/BPM for low current readout was re-designed for g2p
>>> (and also used for QWeak, so it is available in Hall C).
>>> The signal (with noise ratio suppression) was designed to reach
>>> 1% in significantly less than 1s (we wanted to each helicity at 1KHz).
>>> If you want, I can ask our student, Pengjia Zhu and/or Hall A staff
>>> Alexandre Camsonne to give you results.
>>> The absolute calibration is done with the Tungsten calorimeter, which
>>> was designed for 1% precision. We achieved probably slightly worse,
>>> at 1-2% level.
>>>
>>> Cheers.
>>>
>>> Jian-ping
>>>
>>>
>>> On 5/3/2013 1:54 PM, O. A. Rondon wrote:
>>>> Hi JP,
>>>>
>>>> J. P. Chen wrote:
>>>>> 2) For charge determination, it is confusing. Should not say 5%. With the
>>>>> calibration of Tungsten calorimeter, the BCM will have an absolute
>>>>> uncertainty
>>>>> at the level of 1-2%, and relative uncertainty (from one target
>>>>> polarization period
>>>>> to next period) should be better than 1%, depending on the linearity of the
>>>>> BCM response.
>>>>>
>>>> We need to be careful here. Since this is a Hall C proposal, Dave Mack
>>>> will tell you that he cannot calibrate the low current BCM's to better
>>>> than 5% (5 nA at 100 nA). See this hclog entry
>>>> https://hallcweb.jlab.org/hclog/0902_archive/090211140308.html
>>>>
>>>> I think the 1% estimate is reasonable, but it involves integrating over
>>>> time. I believe the charge monitors read every 2s in Hall C. So we'll
>>>> have to accumulate about 25 readings, or one minute, for a 1% delta Q/Q.
>>>>
>>>> I'm sure the Hall A calorimeter will help, but how long does it need to
>>>> integrate at 100 nA for a 1% error?
>>>>
>>>> In any case, we need to be precise about this for the TAC.
>>>>
>>>> Cheers,
>>>>
>>>> Oscar
>>>>
>>>>
>>>>
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>
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